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236 lines
8.0 KiB
236 lines
8.0 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* Routines to manage notifier chains for passing status changes to any |
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* interested routines. We need this instead of hard coded call lists so |
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* that modules can poke their nose into the innards. The network devices |
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* needed them so here they are for the rest of you. |
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* |
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* Alan Cox <[email protected]> |
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*/ |
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#ifndef _LINUX_NOTIFIER_H |
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#define _LINUX_NOTIFIER_H |
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#include <linux/errno.h> |
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#include <linux/mutex.h> |
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#include <linux/rwsem.h> |
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#include <linux/srcu.h> |
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/* |
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* Notifier chains are of four types: |
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* |
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* Atomic notifier chains: Chain callbacks run in interrupt/atomic |
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* context. Callouts are not allowed to block. |
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* Blocking notifier chains: Chain callbacks run in process context. |
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* Callouts are allowed to block. |
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* Raw notifier chains: There are no restrictions on callbacks, |
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* registration, or unregistration. All locking and protection |
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* must be provided by the caller. |
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* SRCU notifier chains: A variant of blocking notifier chains, with |
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* the same restrictions. |
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* |
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* atomic_notifier_chain_register() may be called from an atomic context, |
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* but blocking_notifier_chain_register() and srcu_notifier_chain_register() |
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* must be called from a process context. Ditto for the corresponding |
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* _unregister() routines. |
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* |
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* atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(), |
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* and srcu_notifier_chain_unregister() _must not_ be called from within |
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* the call chain. |
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* |
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* SRCU notifier chains are an alternative form of blocking notifier chains. |
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* They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for |
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* protection of the chain links. This means there is _very_ low overhead |
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* in srcu_notifier_call_chain(): no cache bounces and no memory barriers. |
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* As compensation, srcu_notifier_chain_unregister() is rather expensive. |
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* SRCU notifier chains should be used when the chain will be called very |
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* often but notifier_blocks will seldom be removed. |
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*/ |
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struct notifier_block; |
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typedef int (*notifier_fn_t)(struct notifier_block *nb, |
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unsigned long action, void *data); |
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struct notifier_block { |
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notifier_fn_t notifier_call; |
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struct notifier_block __rcu *next; |
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int priority; |
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}; |
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struct atomic_notifier_head { |
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spinlock_t lock; |
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struct notifier_block __rcu *head; |
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}; |
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struct blocking_notifier_head { |
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struct rw_semaphore rwsem; |
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struct notifier_block __rcu *head; |
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}; |
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struct raw_notifier_head { |
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struct notifier_block __rcu *head; |
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}; |
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struct srcu_notifier_head { |
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struct mutex mutex; |
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struct srcu_struct srcu; |
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struct notifier_block __rcu *head; |
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}; |
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#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ |
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spin_lock_init(&(name)->lock); \ |
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(name)->head = NULL; \ |
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} while (0) |
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#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ |
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init_rwsem(&(name)->rwsem); \ |
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(name)->head = NULL; \ |
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} while (0) |
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#define RAW_INIT_NOTIFIER_HEAD(name) do { \ |
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(name)->head = NULL; \ |
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} while (0) |
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/* srcu_notifier_heads must be cleaned up dynamically */ |
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extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); |
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#define srcu_cleanup_notifier_head(name) \ |
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cleanup_srcu_struct(&(name)->srcu); |
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#define ATOMIC_NOTIFIER_INIT(name) { \ |
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.lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
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.head = NULL } |
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#define BLOCKING_NOTIFIER_INIT(name) { \ |
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.rwsem = __RWSEM_INITIALIZER((name).rwsem), \ |
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.head = NULL } |
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#define RAW_NOTIFIER_INIT(name) { \ |
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.head = NULL } |
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#define SRCU_NOTIFIER_INIT(name, pcpu) \ |
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{ \ |
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.mutex = __MUTEX_INITIALIZER(name.mutex), \ |
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.head = NULL, \ |
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.srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu), \ |
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} |
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#define ATOMIC_NOTIFIER_HEAD(name) \ |
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struct atomic_notifier_head name = \ |
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ATOMIC_NOTIFIER_INIT(name) |
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#define BLOCKING_NOTIFIER_HEAD(name) \ |
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struct blocking_notifier_head name = \ |
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BLOCKING_NOTIFIER_INIT(name) |
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#define RAW_NOTIFIER_HEAD(name) \ |
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struct raw_notifier_head name = \ |
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RAW_NOTIFIER_INIT(name) |
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#ifdef CONFIG_TREE_SRCU |
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#define _SRCU_NOTIFIER_HEAD(name, mod) \ |
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static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \ |
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mod struct srcu_notifier_head name = \ |
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SRCU_NOTIFIER_INIT(name, name##_head_srcu_data) |
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#else |
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#define _SRCU_NOTIFIER_HEAD(name, mod) \ |
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mod struct srcu_notifier_head name = \ |
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SRCU_NOTIFIER_INIT(name, name) |
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#endif |
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#define SRCU_NOTIFIER_HEAD(name) \ |
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_SRCU_NOTIFIER_HEAD(name, /* not static */) |
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#define SRCU_NOTIFIER_HEAD_STATIC(name) \ |
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_SRCU_NOTIFIER_HEAD(name, static) |
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#ifdef __KERNEL__ |
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extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int raw_notifier_chain_register(struct raw_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, |
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struct notifier_block *nb); |
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extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, |
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unsigned long val, void *v); |
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extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
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unsigned long val, void *v); |
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extern int raw_notifier_call_chain(struct raw_notifier_head *nh, |
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unsigned long val, void *v); |
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extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
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unsigned long val, void *v); |
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extern int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh, |
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unsigned long val_up, unsigned long val_down, void *v); |
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extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, |
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unsigned long val_up, unsigned long val_down, void *v); |
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extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, |
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unsigned long val_up, unsigned long val_down, void *v); |
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#define NOTIFY_DONE 0x0000 /* Don't care */ |
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#define NOTIFY_OK 0x0001 /* Suits me */ |
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#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ |
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#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) |
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/* Bad/Veto action */ |
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/* |
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* Clean way to return from the notifier and stop further calls. |
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*/ |
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#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) |
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/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ |
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static inline int notifier_from_errno(int err) |
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{ |
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if (err) |
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return NOTIFY_STOP_MASK | (NOTIFY_OK - err); |
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return NOTIFY_OK; |
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} |
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/* Restore (negative) errno value from notify return value. */ |
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static inline int notifier_to_errno(int ret) |
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{ |
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ret &= ~NOTIFY_STOP_MASK; |
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return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; |
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} |
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/* |
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* Declared notifiers so far. I can imagine quite a few more chains |
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* over time (eg laptop power reset chains, reboot chain (to clean |
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* device units up), device [un]mount chain, module load/unload chain, |
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* low memory chain, screenblank chain (for plug in modular screenblankers) |
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* VC switch chains (for loadable kernel svgalib VC switch helpers) etc... |
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*/ |
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/* CPU notfiers are defined in include/linux/cpu.h. */ |
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/* netdevice notifiers are defined in include/linux/netdevice.h */ |
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/* reboot notifiers are defined in include/linux/reboot.h. */ |
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/* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
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/* Virtual Terminal events are defined in include/linux/vt.h. */ |
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#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
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/* Console keyboard events. |
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* Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and |
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* KBD_KEYSYM. */ |
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#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ |
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#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ |
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#define KBD_UNICODE 0x0003 /* Keyboard unicode */ |
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#define KBD_KEYSYM 0x0004 /* Keyboard keysym */ |
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#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ |
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extern struct blocking_notifier_head reboot_notifier_list; |
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#endif /* __KERNEL__ */ |
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#endif /* _LINUX_NOTIFIER_H */
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